Determination of blood haematocrit and haemoglobin, plasma iron content, total iron binding capacity and phosphoprotein (vitellogenin), and the iron content of different organs (pectoral muscle, liver, spleen, intestine, femur bone marrow, blood, gonad and eggs, and feathers) were carried out in prelaying, onset of laying and full laying females, as well as in adult males. The whole iron content was also determined on incinerated specimens giving these results: 53.7 parts per million (p.p.m.) iron in the prelaying group, 54.5 p.p.m. iron at the onset of laying, 64.3 p.p.m. iron in full laying and 53.5 p.p.m. iron in males. The plumage represented 5-8% of the total body weight, and its iron content oscillated between 152-163 p.p.m. iron in males and non-laying females and 177.3 p.p.m. iron at full laying. The laying period induced important variations in plasma levels and in organ distribution, but not in haematological values. The first eggs laid were smaller (9.2 g) and richer in iron (427 micrograms iron) than those laid by older layers (11.8 g and 305 micrograms iron). The percentage distribution of the total iron content of organs was, in prelaying females: feathers, 21.9; blood, 56.6; pectoral muscle 8.1; liver, 9.7; intestine, 2.7. In laying females: 29.1; 46.6; 11.5; 7.4; 4.2. In males: 17.4; 59.6; 11.4; 7.9; 2.3. The increase in intestinal iron content in laying quails coincided with a double intake of food. This distribution differs from the mammalian model, as egg production (where each egg represented 2.5-5.5% of the total iron) and the great inert iron deposits in the plumage require an elaborate iron metabolism control system to cover all the iron needs in birds.